1. Field of the Invention
The present invention relates to a latent image carrier and an image forming apparatus for employing the latent image carrier; and more particularly to the image forming apparatus having a noise prevention structure in a photorecepter serving as the latent image carrier.
2. Description of the Prior Art
In image forming apparatuses, such as a copier, a facsimile, and a printer, an unfixed image transferred and carried on a recording medium such as a sheet of paper is fixed thereon and formed into a copied object or a printed output.
Charging process is one of the image forming processes that is conducted in an image forming apparatus.
The process is a process of charging a uniform electric charge to a photoreceptor serving as a latent image carrier. However, as the charging method, there is charge or contact charge by corona discharge. Corona discharge is a method in which a corona charger, which is disposed so that a predetermined gap is provided between the photoreceptor and the corona charger; is arranged and a high voltage is applied to a charger wire to thereby perform corona discharge. According to this method, discharged products such as ozone and nitrogen oxide are generated during discharge. As such products bring about environmental deterioration, recently, a contact charge method that can be charged with a low voltage and not generate the above-mentioned drawbacks is being adopted.
According to the contact charging method, a conductive roller, brush, or blade is made to come into contact with the photoreceptor and a voltage is applied therebetween, whereby charge injection can be performed on the photoreceptor.
In the case of the contact charging method, the application of a low voltage is fine and there is no generation of discharge products. However, deposition such as residual toner or the like on the photoreceptor are apt to be reversibly transferred since the charger is in direct contact with the photoreceptor. Moreover, when left unattended for a long period of time, a permanent bend will occur to a portion of the charger member in contact with the photoreceptor causing it to deform. Thus, when the charge process is conducted once more, there may be a change in the status of contact with the photoreceptor. Consequently, there was fear that failure to uniformly contact the photoreceptor will lead to inconsistent charging.
In order to resolve the drawbacks in the above-mentioned contact charging method, a method in which a predetermined microscopic interval is maintained between the photoreceptor and the charging member, what is known as a method of forming a noncontact state charging range between the photoreceptor and the charging member has been proposed. Of the structures employed in this method, there is one in which when a roller is used as the charging member, for instance, a film having a predetermined thickness is wrapped around both of the axial circumferential surfaces of the charging roller, whereby a gap of the microscopic interval can be provided by the thickness of the film.
Maintaining the aforementioned gap of the microscopic interval according to predetermined dimensions is critical to not changing the charging property, In other words, on the assumption that the gap is being maintained, uniform charging can be performed by applying a DC voltage relatively easy to set. However, when there is a change in the size of the gap making it larger than the predetermined gap, a charged potential will change in response to the increasing change thereof. Hence, in the prior art, superimposing AC voltage on the DC voltage is conducted so that a uniform charging property may be attained even if a change in the size of the gap occurs.
A core bar of a relatively light material having conductivity is employed as a structure of the photoreceptor. Specifically, a thinly formed cylinder made of aluminum is used.
There are cases in which noise is generated during an operation in a photoreceptor of such structure. In other words, devices for performing each of the processes of charging, writing, developing, transferring, and cleaning are arranged facing the photoreceptor.
Among these devices, particularly, the charging device and the cleaning device are often the source of generating noise in the photoreceptor.
As is apparent from the aforementioned charging condition, since an AC voltage superimposed on a DC voltage is applied to the charging device, the thin cylindrical part will easily resonate when the AC voltage is applied. The resonance of the thin cylindrical part is the cause of conveying noise to the periphery parts.
A blade in contact with the photoreceptor is provided in the cleaning device. Owing to the repetitious movement of the blade being dragged along with the movement of the photoreceptor and then returning back to its original position, the thin cylindrical part vibrates, causing the photoreceptor to resonate and generate noise.
On the other hand, though a gap of a microscopic interval is formed in the charging device which faces the photoreceptor as in the above structure, when a deformation occurs in the photoreceptor side, that is, if a portion of the circumferential wall thereof dents or swells, the microscopic interval will be altered even if the microscopic interval is maintained on the side of the charging device, thus leading to a change in the charging property. A change in the charging property causes the formation of an abnormal image.
The present invention has been made in view of the foregoing problems in a conventional latent image carrier and image forming apparatus employing the conventional latent image carrier, and therefore has an object to provide a latent image carrier and an image forming apparatus equipped with a structure capable of preventing noise generation and alteration of a gap formed between the latent image carrier and a charging device opposite each other to prevent a change in a charging property thereof from occurring, whereby the prevention of generating an abnormal image can be made in the case where a thin cylindrical body is utilized as the latent image carrier.
To achieve the above object, according to a first feature of the present invention, there is provided a latent image carrier capable of forming an electrostatic latent image which corresponds to an image by means of optical writing after which a photosensitive layer has been uniformly charged, characterized in that the latent image carrier is formed of a thin cylindrical body and deformation preventing member is disposed in the interior portion thereof along the circumferential and axial directions.
According to a second feature of the present invention, the aforementioned deformation preventing member is characterized in that it comprises a base positioned at a shaft of the latent image carrier and at plural places of the base, a plurality of leg parts extending therefrom along the circumferential direction of the latent image carrier with their distal ends elongated towards the interior of the latent image carrier is provided with a bulging portion capable of coming into contact with the inside surface of the latent image carrier.
According to a third feature of the present invention, the aforementioned deformation preventing member is characterized in that it is twisted in the axial direction of the latent image carrier forming successive blade structures from one axial end thereof towards the other axial end thereof.
According to fourth and fifth features of the present invention, the aforementioned deformation preventing member is characterized in that it is formed of an elastic body. In this case, a diameter of said deformation preventing member is greater than an inner diameter of said latent image carrier upon non-elastic deformation of the deformation preventing member.
A fifth feature of the present invention is characterized in that rubber is used as the aforementioned deformation preventing member,
A sixth feature of the present invention is characterized in that the latent image carrier is formed of a rigid body.
According to a seventh feature of the present invention, rubber is used as the deformation preventing member.
According to an eighth feature of the present invention, an Image forming apparatus uses the latent image carrier which has the aforementioned features.